The placement of microprobes into deep brain structures such as hippocampus, Scarpa's ganglion, inferior colliculus, cochlear nucleus and deep cortical layers continues to be a growing area of interest for our external collaborators. Dr. Buzsaki's presentations at national meetings as well as his publications have stirred a great deal of interest from those recording in hippocampus. Challenges in using the probes for these preparations include holding the probe and maintaining a straight trajectory during insertion, accurate site placement in small regions well below the brain surface, and stabilization after insertion. We are working with the listed group of collaborative researchers to solve these problems. Probes with long shanks tend to bend during insertion. Several investigators are using cannular preparations to insert probes into deep structures. Others are exploring the attachment of small, more rigid structures to the back of the substrate. Investigators are now regularly performing successful stereotactic placement of long probes into deep structures using these methods. Custom probes have been designed by the above investigators and have been fabricated and provided by the Center mounted and bonded to desired connectors. The work done within this scientific sub-project benefits many investigators with new placement techniques, not only in deep brain structures but in other areas as well.